This invention relates to tare adjustment apparatus for computing scale systems of the type which includes a scale and a computer for weighing and computing automatically the value of each of successively weighed loads or articles.
A system of the general type to which the invention relates is shown in U.S. Pat. No. 3,741,324. Such a weighing scale includes provision for display of the price per unit weight and the total price or value of goods placed on a scale platform. The weight of the goods is visually displayed by an optical projection arrangement. An optical chart, connected to the scale platform, moves in proportion to the weight of the goods. This chart includes both human recognizable and machine recognizable indicia representing weight. The human recognizable indicia is projected optically for continuous viewing by customers while a photodetector arrangement, in cooperation with the machine recognizable indicia on the chart, provides electronic signals indicating the weight of the goods. This electronic weight information is then multiplied by the price per unit weight information, supplied by the operator through a keyboard, and the resulting value is displayed.
In computing scale systems of the above mentioned type, it is desirable to make tare adjustments compensating for the weight of the container so that the net weight of the goods is accurately measured and the value correctly computed. Prior art computing scale systems have provided tare adjustment mechanisms for this purpose, as shown, for instance, in U.S. Pat. No. 3,037,563. Also, there have been provided previously interlock systems actuated by a change in unit price information to prevent operation of the scale until such time as the operator has physically moved the tare adjustment knob.
Further, as shown in U.S. Pat. No. 3,786,881, there have been provided weighing systems wherein a tare signal light is lit until the operator touches the tare adjustment knob prior to each weighing operation. Thus the operator is made aware of the tare setting before each weighing, even if no tare change is required. Provision is also made to activate the tare signal light if the tare adjustment knob should be touched accidentally during a weighing operation. A problem with such a weighing system is that the operator may be tempted to merely touch the tare adjustment knob before each weighing, even though successive containers vary in size and therefore require different tare settings.